Spec: a small full-stack app with real persistence and auth

The brief

Build a small app where a user creates an account, logs in, and manages a personal list of something — the specific domain matters far less than doing the mechanics for real. Recipes, workout logs, book notes, expense entries — pick something you'd actually plausibly use yourself, since that will keep you motivated past the boring middle part.

Requirements

• Real account creation and login (password hashing done properly, not stored in plain text) — this is the part of the spec that actually matters most; see the previous track's lessons on this if you haven't built auth before.
• Data persists in a real database, not in memory or local storage only.
• A user can only see and modify their own data — not because the UI happens to hide other people's, but because the backend actually enforces it.
• Deployed somewhere reachable by a URL, not just running on your own machine.

Why this is portfolio-worthy

This is the shape of an enormous fraction of real software jobs: accounts, ownership, a database, a deployed URL. Getting all four pieces working together — and being able to explain how ownership is enforced on the backend, specifically — demonstrates something a solo algorithm exercise can't.

What to avoid

Don't spend your limited time on visual polish before the four requirements above are solid — a plain-looking app where auth and ownership are done correctly beats a beautiful one where any logged-in user can edit anyone else's data. That specific bug is also a natural, honest thing to mention if an interviewer asks what you'd improve.